Lizard dives with an 'air tank'

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Lizard dives with an 'air tank'

January 15, 2019 - 14:49
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A lizard that lives next to streams in the mountains of Costa Rica is able to trap pockets of air around it's head and throat. By breathing out a big bubble into these pockets and taking it back in the lizard may be extracting the oxygen essentially allowing it to breathe underwater for a while.

The Water anole (Anolis aquaticus) seem to be able to breathe underwater by using a bubble of air trapped on their nose.

It had previously been thought that the reptiles held their breath when they submerged but in a video a lizard is shown remaining underwater for at least 16 minutes while blowing out and re-inhaling a large bubble of air.

Bubble on the nose

This extraordinary behaviour has been observed and filmed for the first time by ecologist Lindsey Swierk of Binghamton University, New York. “They are probably extracting lower concentrations of oxygen every time they’re respiring the air bubble, but it might just be enough to keep them underwater for long enough that they can escape a threat,” she says. Even though the bubble is relatively large, it remains attached to the lizard’s head rather than floating off to the surface.

The bubble only remains in place for a second before the bulge completely disappears. This process repeats every few seconds as inhalation and exhalation of the air bubble allows for some exchange of fresh air among these air pockets. Several aquatic insects and spiders have special adaptations -some hairy protrusions or other texture combined with a hydrophobic/waxy coating - that allow them to trap a layer of air called a “plastron” to breathe underwater. In some cases, it has been shown that these bubbles actually function as gills — oxygen diffuses into the bubble from the surrounding water while carbon dioxide diffuses out. Whether this is also the case with the lizard it being much larger is another question

Diffusion? 

In moving water, such at the stream in which this lizard lives, there may be some re-oxygenation of the bubble air by diffusion from the water. In the absence of significant gas exchange between the water and the air bubble in between breaths, the bubble trick could also be a way of suppressing a breathing reflex in the lizards.

There may be alternative explanations and a diving duration of 16 minutes does not seem too long taking into account a dive response, the lower temperature and lower metabolic rates of reptiles and a high anaerobic capacity indicated by lactate accumulation.

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